Ratification is a principal's legal confirmation of an act of its agent. In international law, ratification is the process by which a state declares its consent to be bound to a treaty. In the case of bilateral treaties, ratification is usually accomplished by exchanging the requisite instruments, and in the case of multilateral treaties, the usual procedure is for the depositary to collect the ratifications of all states, keeping all parties informed of the situation.

The institution of ratification grants states the necessary time-frame to seek the required approval for the treaty on the domestic level and to enact the necessary legislation to give domestic effect to that treaty. The term applies to private contract law, international treaties, and constitutions in federal states such as the United States and Canada. The term is also used in parliamentary procedure in deliberative assemblies.

In contract law, the need for ratification often arises in two ways: if the agent attempts to bind the principal despite lacking the authority to do so; and if the principal authorizes the agent to make an agreement, but reserves the right to approve it. An example of the former situation is an employee not normally responsible for procuring supplies contracting to do so on the employer's behalf. The employer's choice on discovering the contract is to ratify it or to repudiate it.

The latter situation is common in trade union collective bargaining agreements. The union authorizes one or more people to negotiate and sign an agreement with management. A collective bargaining agreement can not become legally binding until the union members ratify the agreement. If the union members do not approve it, the agreement is void, and negotiations resume.

A deliberative assembly, using parliamentary procedure, could ratify action that otherwise was not validly taken. For example, action taken where there was no quorum at the meeting is not valid until it is later ratified at a meeting where a quorum is present.

The ratification of international treaties is always accomplished by filing instruments of ratification as provided for in the treaty. In many democracies, the legislature authorizes the government to ratify treaties through standard legislative procedures by passing a bill.

In Australia, power to enter into treaties is an executive power within Section 61 of the Australian Constitution so the Australian Government may enter into a binding treaty without seeking parliamentary approval. Nevertheless, most treaties are tabled in parliament for between 15 and 20 joint sitting days for scrutiny by the Joint Standing Committee on Treaties, and if implementation of treaties requires legislation by the Australian parliament, this must be passed by both houses prior to ratification.[1]

The President makes a treaty in exercise of his executive power, on the aid and the advice of the Council of Ministers headed by the Prime Minister, and no court of law in India may question its validity. However, no agreement or treaty entered into by the president is enforceable by the courts which is incompatible with Indian constitution/ national law, as India follows dualist theory for the implementation of international laws.